Image transfer process



Unite 3,060,022 Patented Oct. 23, 1962 ice The present invention relates to a substantially dry image transfer process, and more particularly to such a process in which photopolymerization of an unsaturated organic compound by a silver compound initiator plays a significant role.

Two image transfer methods are currently being commercialized for the production of a duplicate copy from an original. One of these methods, described in Rott, U.S. :Patent 2,352,014, dated June 20, 1944, involves the transfer of unexposed silver halide from an exposed light sensitive element to a non-light sensitive receiving sheet in the presence of an organic silver halide develop ing agent, a silver halide solvent and a fogging agent. This process is generally referred to as a diffusion transfer process.

The other method relies upon the use of a slightly hardened silver halide emulsion containing a tanning developer and a dye or pigment and a non-light sensitive receiving sheet of paper or the like. In this process, the Silver halide emulsion, after exposure under a pattern, is tanned developed in an alkali after which the developed layer is forced against the receiving sheet. Part of the unexposed emulsion is thus physically transferred imagewise to the receiving sheet. It is clear that several copies ban be made from the single light sensitive ele ment by this process and, to this extent, the process has an advantage over the diffusion transfer process by which only one copy can be made from one light sensitive element.

Both of these procedures, since they allow direct copying from translucent or opaque originals, have received Wide customer acceptance. However both processes suffer from the disadvantage that they include usual photographic processing steps requiring aqueous solutions. They are, therefore, typical Wet processes needing special equipment for handling the processing solutions.

I have now found a substantially dry method of image transfer based on imagewise photopolymerization of a monomer containing the grouping =CH =C= with a silver salt initiator, the physical transfer of unexposed monomer and related initiator to a receiving sheet coated with an amphoteric metal oxide and the printing out of the silver in the receiving sheet to give sharp dark-colored images of print-out silver. Manifestly, this process permits the production of multiple copies since only a small amount of monomer containing silver ion is required to give a sharp dark image. Furthermore, since photographic processing baths are not required, the apparatus for conducting the process may be of the simplest nature.

Said process constitutes the purposes and objectsof my invention;

The process, in its general aspects, is carried out by exposing underneath a pattern a light sensitive photographic element comprising a :base, preferably translucent, coated with a photographic colloid containing a water soluble monomer having the grouping CH =C= and a silver compound initiator. A receiving sheet is provided by coating a base with a photographic colloid containing an amphoteric metal oxide, such as zinc oxide, titanium dioxide, zirconium dioxide or silicon dioxide. The receiving sheet, prior to use, is preferably dampened with water. Exposure of the light sensitive element induces photopolymerization in the imaged areas with the formation in such areas of a hard polymeric mass. Concolloids, such as gelatin,

tact of the receiving sheet with the exposed light sensitive element causes a physical transfer of a small amount of the photographic colloid and associated monomer and silver compound initiator. By exposing the receiving sheet to white light or U.V. light, the monomer is hardened. In the interim, the transferred silver compound reacts with the amphoteric metal oxide to give a positive image. If desired, the color of the image may 'be mod- I ified by employing in the receiving sheet an anti-plum ming agent or a photographic toning agent.

The base for the light sensitive element may be paper or photographic film, such as cellulose triacetate, polyethylene terephthalate, polycarbonate or the like. The base should be transparent or translucent when a reflexwise exposure.

The base is coated with any of the usual photographic polyvinyl alcohol, methyl cellulose, casein, glue or the like. The nature of the water soluble colloid is not critical Since it merely serves as a carrier for the monomer and the silver compound initiator.

Any water soluble monomer containing the grouping CH =C= may be employed. Examples of such monomers are acrylamide; acrylic acid; N-ethanol acrylamide; methacrylic acid; calcium acrylate; methacrylamide; vinyl pyrrolidone; vinylmethyl ether or the like. It is to be understood that these are merely examples and that any water soluble compound containing the aforesaid unsaturated group is suitable.

The silver compound initiator may be any radiation sensitive silver salt, such as silver nitrate; silver acetate; silver benzoate; silver carbonate; silver chloride; silver bromide; silver iodide; silver benzenesulfinate; silver citrate; silver nitrite; silver salicylate; silver sulfamate; silver sulfate; silver tartrate; silver sulfite; silver eosinate; silver erythrosinate; silver lactate; silver phenolsulfonate; silver laurate or the like.

A slight hardening of the colloidal carrier of the light sensitive element is desirable and, to this end, there may be added a small amount of formaldehyde or chrome alum.

Dispersion of the ingredients in the colloidal carrier is facilitated by use of a surface active agent and for this purpose there may be used lauryl sulfonate, the addition product of oleyl alcohol and ethylene oxide, condensationproducts of long chain fatty acids, such as stearic acid or palmitic acid with N-methyl-taurine, or the like. All of these are commercial products readily available on the open market.

It is recognized that the molecular weight and, hence, the ultimate hardness of the polymer can be increased by utilization during polymerization of a small amount of an unsaturated compound containing at least two terminal vinyl groups each linked to a carbon atom in a straight chain or in a ring. These compounds serve to cross link the polymeric chains and are generally designated as cross-linking agents. Such agents are described, for example, by Kropa and Bradley in vol. 31, No. 12, of Industrial and Engineering Chemistry, 1939. Examples of such cross-linking agents are N,N'-methylenebis acrylamide; triallyl cyanurate; divinyl benzene; divinyl ketones and diglycol diacrylate.

The cross-linking agent is generally used in an amount of from 10 to 50 parts of monomer to each part of crosslinking agent.

In preparing the coatings, the components are dissolved in water, coated on the base in the usual fashion and dried. Generally, for each part of the monomer, there is employed .3 to 1 part of colloidal carrier and from .05 to .5 part of silver compound initiator. The quantity of hardening agent and surfactant is rather small. Typically, for 6 parts of monomer, there may be used as little making as .05 gram of chrome alum or an equivalent amount of formaldehyde. Similarly, for the same amount of monomer, there will be used about .10 to .15 gram of dispersing agent. i i

The receiving sheet is made by dispersing in water a colloidal carrier and the amphoteric metal oxide, along with a small amount of a dispersing agent, and coating the same on the base. Usually, the ratio beween the amphoteric metal oxide and the colloidal carrier amounts to about 1 part of oxide to about .03 to .08 part of the colloidal carrier. "In order to ensure production of black silver images on the receiving sheet, it is preferred to include in such sheet anti-plumming agents, such as benzotriazole; mercaptotetrazole; 5-mercapto-1,2,4-triazole or photographic toning agents, such as chlorobenzotriazole; quinoline; diphenyl iodinium nitrate; rhodamine; pseudothiohydantoin and the like.

The emulsion coating on the base of the light sensitive element usually has a thickness of 5-l5 microns. On the other hand, the coating'on the receiving sheet will range from about 5 -30 microns. It is clear that with an emulsion layer of the stated thickness on the light sensitive element, numerous copies can be obtained by repetition of the process with the same light sensitive element.

The invention will be further illustrated by the fol lowing examples, but it is to be understood that the invention is not restricted thereto.

7 Example I A light sensitive element was made by coating a paper base with the following composition:

.Cc. Gelatin, 12.5 A-5 10.0 Silver nitrate, 68% 1.0 Chrome alum, 10% .05 Lauryl sulfonate, .5

The coating was then dried. NoTE.-A-5 is compounded as follows:

Acrylamide rams 180 N,N'-methylenebis acrylamide do 7 Water cc 120 A receiving sheet for use with this light sensitive ele ment was prepared by coating a paper base with the following composition:

Water cc 3.0 Titanium dioxide grams 2.5 Gelatin, 5% ..cc 30.0 Saponin, 8% cc .6

This coating was then dried.

The light sensitive element was exposed under a pattern to a 375-watt photofiood lamp for 40-60 seconds at a distance of 12 inches. This led to the photopolymerization of the acrylamide in the exposed areas to a hard polymeric mass.

The exposed light sensitiveelement is then pressed into contact with the receiving sheet, preferably after moistening the latter. After peeling the light sensitive element away, there is transferred to the receiving sheet Example II An exposure material was made by coating a paper base with the following composition:

Gelatin, 10% cc l5 A-5 cc 8 Silver nitrate, 68% cc 1 Citric acid gram" 1 Chrome alum, 10% cc .1 Lauryl sulfonate, 25% cc .5

It is clear that in this light sensitive element, silver citrate is present.

Exposure of the light sensitive element and its contact with the receiving sheet of Example I yielded duplicates of the original.

Example IV The procedure is the same as in Example III, excepting that the receiving sheet was made by coating a paper base with the following composition:

Water cc 3 Zinc oxide rams 3 Gelatin, 5% cc 25 Saponin, 8% cc .6

Example V The procedure is the same as in Example I, excepting that the gelatin was replaced by an equivalent quantity of polyvinyl alcohol.

The results were similar to those obtained in Example 1.

An exposure material was made by coating a paper base with the following composition:

Gelatin, 10% cc 25 Standard silver chloride photographic emulsion grams 2 A-5 cc 3 Lauryl sulfonate, 25% cc .2 Glycerin cc.. 25

After drying, the coating was exposed under a pattern as in Example I for a period of 30 seconds. The exposed light sensitive element was then pressed into contact with the receiving sheet of Example I, preferably after moistening the latter. After peeling apart and exposing the receiving sheet to white light, images which are duplicates of the original are obtained.

Modifications ,of the invention will occur to personsskilled in the art and I, therefore, do not intend to be limited in the patent granted except as necessitated by the appended claims.

I claim:

l. A dry process of photo-reproduction which comprises exposing to light under a pattern a light sensitive element comprising a base coated with a colloidal carrier, a water soluble photopolymerizable monomeric compound containing a CH =C= group and, as the initiator for photopolymerization, a radiation sensitive silver salt to effect photopolymerization of the exposed areas to a solid polymeric mass, pressing the exposed light sensitive elment into contact with a receiving sheet coated with an amphoteric metal oxide selected from the class consisting of zinc oxide, titanium dioxide, zirconium dioxide and silicon dioxide to transfer imagewise minute amounts of monomer and initiator to the receiving sheet, separating the receiving sheet from the light sensitive element and exposing the receiving sheet to light to print out a dark silver image.

2. The process as defined in claim 1, wherein the monomeric compound is acrylamide.

'3. The process as defined in claim 1, wherein the monomeric compound is acrylamide and the initiator is silver nitrate.

4. The process as defined in claim 1, wherein the base is translucent and exposure is refiexwise.

5. The process as defined in claim 1, wherein the coating on the receiving sheet is zinc oxide.

6. The process as defined in claim 1, wherein the monomeric compound is calcium acryl-ate.

7. The process as defined in claim 1, wherein an antiplumming agent is included in the receiving sheet.

8. The process as defined in claim 1, wherein a toning agent is is included in the receiving sheet.

References Cited in the file of this patent UNITED STATES PATENTS 2,380,280 Weyerts July 10, 1945 2,563,342 Land Aug. 7, 1951 2,596,756 Yutzy et al. May 13, 1952 2,661,331 Howard Dec. 1, 1953 2,699,393 Weyde Jan. 11, 1955 2,716,059 Yutzy et al. Aug. 23, 1955 2,738,319 Kern Mar. 13, 1956 2,756,143 Murray July 24, 1956 2,875,047 Oster Feb. 24, 1959 2,878,121 Gray Mar. 17, 1959 

1. A DRY PROCESS OF PHOTO-REPRODUCTION WHICH COMPRISES EXPOSING TO LIGHT UNDER A PATTERN A LIGHT SENSITIVE ELEMENT COMPRISING A BASE COATED WITH A COLLOIDAL CARRIER, A WATER SOLUBLE PHOTOPOLYMERIZABLE MONOMERIC COMPOUND CONTAINING A CH2=C= GROUP AND, AS THE INITIATOR FOR PHOTOPOLYMERIZATION, A RADIATION SENSITIVE SILVER SALT TO EFFECT PHOTOPOLYMERIZATION OF THE EXPOSED AREAS TO A SOLID POLYMERIC MASS, PRESSING THE EXPOSED LIGHT SENSITIVE ELEMENT INTO CONTACT WITH A RECEIVING SHEET COATED WITH AN AMPHOTERIC METAL OXIDE SELECTED FROM THE CLASS CONSISTING OF ZINC OXIDE, TITANIUM DIOXIDE, ZIRCONIUM DIOXIDE AND SILICON DIOXIDE TO TRANSFER IMAGEWISE MINUTE AMOUNTS OF MONOMER AND INTITIATOR TO THE RECEIVING SHEET, SEPARATING THE RECEIVING SHEET FROM THE LIGHT SENSITIVE ELEMENT AND EXPOSING THE RECEIVING SHEET TO LIGHT TO PRINT OUT A DARK SILVER IMAGE. 